Dual-descriptor-guided design of electric field-sensitive solubilizing additive for stable lithium metal batteries

Abstract

Electrolyte additive has shown great power for improving the stability of lithium metal batteries.However, the weak ion dissociation of additives in carbonate electrolytes and the limited modification effect at cathode side, severely hinder their practical use in full cells. Herein, we present an "electric field-sensitive solubilizing additive (EFSSA)" strategy for rational electrolyte design, employing cubic electrophilicity index (CEPI) and Mulliken charge as dual descriptors for additive screening. As a typical example, the ion dissociation of lithium nitrate (LiNO3) in carbonate electrolyte is largely enhanced by employing tris(trimethylsilyl) borate (TMSB) as a secondary solubilizing additive with a high CEPI. Moreover, TMSB with a high Mulliken charge facilitates the reconstruction of a beneficial anion-dominated solvation structure at the cathode electric double layer via electric field-induced repulsion. Through this synergistic interaction between LiNO3 and TMSB, the ionic conductivity and stability of electrode-electrolyte interface are significantly improved both at anode and cathode sides.The designed LiNO3 -TMSB/carbonate electrolyte enables stable, long-term cycling in Li||Cu cell for > 700 cycles and enables Li||NCM811 full cell to retain 84.6% of its capacity after 600 cycles, with its feasibility further validated in Ah-level pouch cells. This EFSSA strategy and dual descriptors provide conceptual advances for high-performance electrolyte design and propel the practical application of high-energy lithium metal batteries.